Destroying a Planet - How Much Energy?

[lpetrich]

In some science-fiction productions, we find the ability to destroy planets and sometimes even stars. Not just make planets' surfaces uninhabitable, but outright destroy them, turning them into expanding clouds of fragments and dust.

Mundicide | Wookieepedia | Fandom - lists several destroyed planets in the Star Wars universe, notably Alderaan: Destruction of Alderaan | Wookieepedia | Fandom near the beginning of the first Star Wars movie, A New Hope. There is a clip of that event at Star Wars A New Hope - The Destruction of Alderaan - YouTube

Star Trek also has some destroyed planets, like the victims of the Planet killer | Memory Alpha | Fandom (TOS "The Doomsday Machine") and in the Kelvin timeline, the Destruction of Vulcan | Memory Alpha | Fandom (first Star Trek film in that timeline)

How feasible is it to destroy a planet? One must give it more than its  Gravitational binding energy or self-energy.

For the Earth, that is a LOT. I calculate that it takes 2.35*10³² joules to destroy it. Using E = mc^2, that's about 2.62 trillion metric tons of energy. But it is only 4.38*10^-10 times the mass of our homeworld, however. Nevertheless, it is roughly 1/300 of the mass of the Big Island of Hawaii, and it is roughly comparable to the mass of Mt. Everest.

Humanity currently consumes energy at about 18 terawatts, and it would take 400 billion years for us to destroy our homeworld at that rate of consumption.

Using all the sunlight that falls on the Earth's surface would give some 43 million years, however.

For chemical reactions, close to the best case in energy per unit mass of reagents is hydrogen and oxygen, often used as a rocket fuel for that reason. The total amount needed, at 100% efficiency, is about 3 times the Earth's mass. That's because the mass-energy fraction of this reaction is 1.49*10^-10.

Nuclear reactions do much better. Nuclear fission typically releases about 10^-3 of its fuel's mass as energy, meaning that one would need nearly 3 quadrillion tons of uranium. The total production of uranium has been only 3.06 million tons, however, a billion times less. So one would need a cube of uranium 50 km on each side, while the amount that has been mined is only 50 m on each side.

So it ought to be evident that destroying a planet is very hard to do.

 

[Loren Pechtel]

In practice you will almost certainly need a lot more energy than that to make a planet go boom because you won't be able to apply it efficiently. To get away with anything like that amount of energy I would figure you need to fire neutronium and anti-neutronium pellets at each other impacting at the center of the planet. They'll need to be moving near lightspeed to keep from coming apart too badly as they go.

 

[bilby]

The whole business seems like overkill.

Biospheres are fragile; Rendering a planet uninhabitable is pretty easy, and should be sufficient for almost any purpose.

If you want to get a planet out of the way, it's better and cheaper to accelerate it into a difficult orbit (or even to its parent star's escape velocity) than to blow it up - and acceleration leaves the original orbit clearer of rubble and debris.

If you want to kill its population, just drop a large-ish asteroid on it.

 

[lpetrich]

Reviewing Star Wars A New Hope - The Destruction of Alderaan - YouTube it seems very naive, though it is likely not much worse than a lot of other visual-media SF on spaceflight. Like explosions that make sounds and visible ray-gun rays and spacecraft that are never upside down. I remember Gene Roddenberry, creator of ST:TOS, once saying that he did those sorts of things to avoid confusing the audience too much. He explained that a soundless explosion might make people think that the sound had gone off.

Let's look at the destruction of Alderaan more closely. The planet gets vaporized and expands to twice its original size in only a second. How feasible is that? If one destroys a planet with a quick injection of energy, one will want more than is necessary to have some margin of error. If one uses twice the necessary energy on the Earth, our homeworld's fragments will separate at some 10 kilometers per second. That means about 10 minutes to travel an Earth radius.

A 10-minute explosion would be realistic, but it wouldn't be very dramatic.

To go that distance in 1 second, one needs about 1000 times faster, and a million times the energy to be injected.

I'll next consider temperature. Alderaan looked orangish, which is typical of fire and chemical-explosion temperatures, but is it realistic?

I calculated how hot the Earth would get if the amount of waste heat was comparable to the amount of self-energy. Ignoring ionization, I found nearly 100,000 K. The Earth material would not get nearly as hot, because after more than a few thousand K, it becomes hot enough to start stripping electrons, and those increase the specific heat quite a bit. Each electron is like an extra atom, and with each atom losing one electron, I find 100,000 K / (2 particles) or 50,000 K. With two electrons stripped, it's 3 particles, giving around 30,000 K. Eventually this reaches a point where it is not hot enough to strip any more electrons.

Wikipedia has  Ionization energies of the elements (data page) and the ionization energies increase rather fast. I also found Atomic Spectra Database | NIST - with increasing temperature electrons become excited before they get stripped off.

But even with some electrons stripped, the temperature would be well in the blue-hot range, and there wouldn't be the shower of particles that one sees in that clip.

But if one injects a million times more energy, then the temperature would get to well over 10⁹ K, even with all the electrons being stripped off of their atoms.

 

[lpetrich]

Turning to Star Trek, the obvious one is The Original Series "The Doomsday Machine". Our heroes are up against a monster machine that travels through interstellar space and destroys planets. Doomsday Machine: Remastered VFX Comparison - YouTube and  he Doomsday Machine (Star Trek: The Original Series) and Remaster | Memory Alpha | Fandom and RETROSPECTIVE: The Original Series Remastered Project – TrekMovie.com

At one point, it attacks with a beam that is described as pure antiprotons. It would be hard to collimate such a beam, because antiprotons electrically repel each other. But that aside, antimatter is the most efficient choice for delivering energy to destroy a planet -- its energy yield is nearly twice its E = mc^2 value, since it annihilates with ordinary matter. I say "nearly" because a little bit of its energy comes off as neutrinos, and those are only weakly interacting. Those neutrinos are produced indirectly, from proton and neutron annihilation reactions producing charged pions, which decay into muons, which in turn decay into electrons. Decaying into muons and electrons is what makes those neutrinos.

 

[lpetrich]

The whole business seems like overkill.

I agree.

Biospheres are fragile; Rendering a planet uninhabitable is pretty easy, and should be sufficient for almost any purpose.

I'll now consider how much energy is necessary to strip away a planet's atmosphere.

The Earth's atmosphere has a mass of 5.15*10¹⁸ kg, and its oceans a mass of 1.35*10²¹ kg.

Using the Earth's escape velocity gives energies 3.32*10²⁶ and 8.47*10²⁸ joules, or from E=mc^2, 3.59*10⁹ and 9.42*10¹¹ kg.

Using humanity's entire energy output gives 500 thousand and 130 million years, while using the Sun's light flux at the Earth gives 60 and 15,000 years.

This, I think, an overly pessimistic estimate, because the atmosphere and the ocean can be removed by heating them enough to evaporate into space: at least a few thousand K to around 10,000 K. With enough temperature, it becomes probable for air molecules to get kicked up to escape velocity near the top of the atmosphere.

 

[Bomb#20]

How feasible is it to destroy a planet? ... So it ought to be evident that destroying a planet is very hard to do.

Right? You'd think if you have an illudium q-36 explosive space modulator you'll be fine, but turns out it's harder than it looks...

 

[bilby]

The whole business seems like overkill.

I agree.

Biospheres are fragile; Rendering a planet uninhabitable is pretty easy, and should be sufficient for almost any purpose.

I'll now consider how much energy is necessary to strip away a planet's atmosphere.

The Earth's atmosphere has a mass of 5.15*10¹⁸ kg, and its oceans a mass of 1.35*10²¹ kg.

Using the Earth's escape velocity gives energies 3.32*10²⁶ and 8.47*10²⁸ joules, or from E=mc^2, 3.59*10⁹ and 9.42*10¹¹ kg.

Using humanity's entire energy output gives 500 thousand and 130 million years, while using the Sun's light flux at the Earth gives 60 and 15,000 years.

This, I think, an overly pessimistic estimate, because the atmosphere and the ocean can be removed by heating them enough to evaporate into space: at least a few thousand K to around 10,000 K. With enough temperature, it becomes probable for air molecules to get kicked up to escape velocity near the top of the atmosphere.

You needn't strip off the atmosphere and oceans to destroy the biosphere.

Raising their temperature to a point above the temperature at which life can survive is sufficient.

If you want to kill all complex organisms, including humans, raising the temperature of our atmosphere above about 38°C should easily suffice. Killing the oceans would require more energy, but a lower temperature target, for complex life to be eliminated.

Killing everything, including extremophile bacteria, would require higher temperatures, but still lower than those needed to evaporate the entire oceans and atmosphere into space.

 

[lpetrich]

If one strips the air, then our planet will get a new atmosphere, though a rather thin one.

Water - Saturation Pressure vs. Temperature - the oceans will boil until enough of their water has boiled off to go into equilibrium. The vapor pressure of water: 0 C - 0.006 bar, 10 C - 0.012 bar, 20 C - 0.023 bar, 30 C - 0.042 bar -- 100 C - 1.014 bar (actual sea-level pressure)


Temperatures of a few thousand K should be enough to sterilize all the biosphere except for Earth-interior organisms, which would be protected by hundreds of meters of rock overhead. Scientists identify vast underground ecosystem containing billions of micro-organisms | Geology | The Guardian

 Strain 121 - a microbe that can grow at 121 C at deep-ocean pressures.

The thermal limits to life on Earth | International Journal of Astrobiology | Cambridge Core

"Most hyperthermophiles utilize inorganic redox reactions as the sources of energy, and CO2 as the sole carbon source." -- hyperthermophile: optimal growth temperature >~ 80 C.

The current record for a high-temperature growth is Methanopyrus kandleri, originally isolated from a vent in the Gulf of California and found to grow between 84 and 110 °C (Huber et al. Reference Huber, Kurr, Jannasch and Stetter1989; Kurr et al. Reference Kurr, Huber, König, Jannasch, Fricke, Kristjansson and Stetter1991). However a strain of M. kandleri isolated subsequently from the Kairei vent field on the Central Indian Ridge was found to grow at 122 °C under 40 MPa pressure (Takai et al. Reference Takai, Nakamura, Toki, Tsunogai, Miyazaki, Miyazaki, Hirayama, Makagawa, Nunoura and Horikoshi2008), just surpassing the previous record for 121 °C for Geogemma barossii strain 121 (Kashefi & Lovley Reference Kashefi and Lovley2003).

Microbes growing at the very highest growth temperatures all appear to be archaeans, but there are some bacteria are able to grow to ∼100 °C, with the current record being Geothermobacterium ferrireducens, which was isolated from Obsidian Pool in Yellowstone National Park (Kashefi et al. Reference Kashefi, Holmes, Reysenbach and Lovley2002). Two other taxa, Aquifex aeolicus and Thermotoga maritima can grow at 90 °C or above (Table 3), and there are a range of Fe(III)-reducing thermophilic bacteria with T L values in the range 65–75 °C (Sokolova et al. Reference Sokolova, Hanel, Onyenwoke, Reysenbach, Banta, Geyer, Gonzáles, Whitman and Wiegel2006).

So if one heated the atmosphere and the oceans up to 100 C, just about everything would be dead except for organisms much like the earliest organisms on our planet.

 

[lpetrich]

For heating up from 15 C to 100 C, I find energies of 3.1*10²³ J for the atmosphere and 4.8*10²⁶ J for the oceans.

For 20 terawatts of energy rate, that gives 500 years and 760,000 years.

The highest known temperature for an oxygenic-photosynthesis organism is 73 C for a cyanobacterium - Photosynthetic temperature adaptation during niche diversification of the thermophilic cyanobacterium Synechococcus A/B clade | The ISME Journal

So going above that temperature will mean that only methanogens and iron-oxide eaters and the like will survive -- organisms with the earliest sorts of energy metabolism.

The highest T L for a unicellular eukaryote appears to 55–56 °C, which is the upper limit for the rhodophyte Cyanidium caldarium, although optimal (maximum) growth was at 45 °C (Doemel & Brock Reference Doemel and Brock1970, Reference Doemel and Brock1971).

Rhodophytes = red algae

Slightly higher temperatures appear to be tolerated by filamentous fungi, and a survey of a range of high-temperature habitats revealed species able to grow at 55–60 °C (Tansey & Brock Reference Tansey and Brock1972).

...
Higher plants can be found growing close to hot springs in Yellowstone, and in the perennial grass Dichanthelium lanuginosum (intriguingly named ‘hot springs panic grass’) the thermal tolerance is mediated through a mutualistic endophytic fungus Curvularia protuberata (Redman et al. Reference Redman, Sheehan, Stout, Rodriguez and Henson 2002) and a mycovirus (Márquez et al. Reference Márquez, Redman, Rodriguez and Roosinck 2007). With both the fungus and mycovirus present, plants can grow in soils up to 65 °C; with either missing the plants are unable to grow above 38 °C (Márquez et al. Reference Márquez, Redman, Rodriguez and Roosinck 2007).

 

[lpetrich]

Hot springs also provide the hottest habitats inhabited by invertebrates and vertebrates. Temperature in these springs may reach over 50 °C, and the fauna includes crustaceans, chironomid larvae, nematodes and molluscs, as well as fish. It is difficult to establish T L values for these; although many secondary and anecdotal sources quote a range of temperatures for hot springs, there are very few primary sources with data for both temperature and fauna.

...
The highest temperature for completion of the life cycle in an invertebrate may be for nematodes of the genus Aphelenchoides and Panagrolaimus, which tolerate temperatures of 60 °C in compost heaps (Steel et al. Reference Steel, Verdoodt, Čerevková, Couvreur, Fonderie, Moens and Bert 2013).

Vertebrates?

Hot springs also support populations of fish, and the classic high-temperature fish are the desert pupfish of the genus Cyprinodon. These fish live in shallow geothermal springs, where the temperatures are high but vary both spatially and throughout the day and with season. Cyprinodon pachycephalus from the hot springs of San Diego de Alcalá, Chihuahua, México lives in waters of 39.2–43.8 °C (Minckley & Minckley Reference Minckley and Minckley 1986; Miller et al. Reference Miller, Minckley and Norris 2005), and Cyprinodon julimes recently described from the hot springs of Julimes, Chihuahua, México lives at temperatures of between 38 and 46 °C (Montejano & Absalόn Reference Montejano and Absalón2009).

Then hydrothermal-vent animals.

The most studied vent animal in this regard is the Pompeii worm, Alvinella pompeiana. This polychaete lives in a tube through which vent fluids pass, and from which it emerges to forage. Recordings with a temperature probe indicated that at the base of the tube the temperatures can reach 81 °C, and that the base of the worm itself the temperature averaged 61 °C, although occasionally spikes up to 81 °C were recorded.

Then about how some proteins get denatured at 45 C - 50 C.

These data would indicate that in the long term, Alvinella is limited to temperatures below ∼50 °C (Desbruyères & Laubier Reference Desbruyères and Laubier1991). A recent study (Ravaux et al. Reference Ravaux, Hamel, Zbinden, Tasiemski, Boutet, Léger, Tanguy, Jollivet and Shillito2013) has shown that long-term survival, as assessed by a 2 h ramped thermal exposure, is above 42 °C but below 50 °C. Similarly, another vent polychaete Paralvinella sulfinicola, can be found in waters up to 88 °C, but has an upper incipient lethal temperature (at which 50% of the population cannot survive indefinitely) of only 45 °C (Dilly et al. Reference Dilly, Young, Lane, Pangilinan and Girguis 2012).

 

[lpetrich]

Some deserts get very hot, but some animals are still active in them, like ants.

For example, the Saharan silver ant Cataglyphis bombycina forages for very short periods in air temperatures up to 55 °C (Wehner et al. Reference Wehner, Marsh and Wehner 1992). Similarly, Ocymyrmex barbiger, an ant from the Namib Desert, forages in air temperatures up to 67 °C (Marsh Reference Marsh 1985), and the pseudoscorpion Eremogarypus perfectus only goes into heat coma at 65 °C (Heurtault & Vannier Reference Heurtault and Vannier1990).

...
Some such as land snails simply have to sit it out. The desert snail Sphicterochila boisseri minimizes its body temperatures by having a highly reflective shell, which allows it to maintain a tissue temperature of 50 °C in direct sunlight despite a local air temperature of 43 °C and a surface temperature of 65 °C (Schmidt-Nielsen et al. Reference Schmidt-Nielsen, Taylor and Shkolnik 1971).

Turning to land plants,

The record appears to be held by the cactus Opuntia, several species of which can reach internal temperatures up to 65 °C (Smith et al. Reference Smith, Didden-Zopfy and Nobel1984).

Then a lot of discussion of what molecular features make these limits. Too high temperatures and molecules may get into the wrong shapes, may separate from each other, and may even fall part. That's what happens to egg-white proteins when one cooks an egg.

 

[bilby]

The more I look at this, the more it seems to require more energy and time than it's really worth.

Let's not do it.

At least, not this year.

 

[Swammerdami]

There's a good WWII movie about blowing up a German dam. After detonating some explosives, one of the team is dejected. "We failed. All we got were some tiny holes." The expert laughs and says "You thought you could destroy that dam with a hundred pounds of explosives? Of course you couldn't. But millions of tons of water will destroy that dam." And sure enough, the tiny holes get bigger and bigger as water rushes through. The dam collapses.

Find a way to harness the planet's molten core, or a way to redirect its rotation. Let that core destroy the planet.

 

[Jimmy Higgins]

Can't you just place a large (very large) cast iron pan along it's orbit?

I'd imagine that it'd be easier to manipulate the Earth's orbit to fall into the Sun (or maybe even easier to eject from the solar system), than use energy to destroy the planet.

 

[Elixir]

Can't you just place a large (very large) cast iron pan along it's orbit?

I'd imagine that it'd be easier to manipulate the Earth's orbit to fall into the Sun (or maybe even easier to eject from the solar system), than use energy to destroy the planet.

Wouldn’t it be sufficient to render it uninhabitable by humans? A minor alteration of its solar orbit should do the trick. What is the need to destroy the whole thing?

 

[Jimmy Higgins]

Can't you just place a large (very large) cast iron pan along it's orbit?

I'd imagine that it'd be easier to manipulate the Earth's orbit to fall into the Sun (or maybe even easier to eject from the solar system), than use energy to destroy the planet.

Wouldn’t it be sufficient to render it uninhabitable by humans? A minor alteration of its solar orbit should do the trick. What is the need to destroy the whole thing?

It is a thought experiment, looking into space fantasy movies and just what would be required to destroy a planet, including its tootsie center. Hence a large (very large) cast iron pan placed along the orbit of a planet to run into .

I think the issue noted in the OP is just the gargantuan amount of power required to destroy a planet. After all, planets are pretty big, even the small ones. Maybe we should look to another source regarding destroying heavenly bodies. We've already done it... not that it wasn't controversial.

 

[Bomb#20]

What is the need to destroy the whole thing?

Practice.

 

[bilby]

I say we think bigger.

Let's blow up the Sun.

"For years, mankind has yearned to destroy the Sun" - C. Montgomery Burns

My plan is to use the hydrogen and other light elements already present to make a massive thermonuclear explosion.

Of course, the Sun is fairly big, so it might take a little while; I estimate around eight billion years. But the explosion should be close to being big enough to destroy the Earth (in about five billion years time). And it will destroy Mercury and Venus too, as a bonus.

 

[lpetrich]

Not a very efficient method, and it won't even make much of an explosion, if it can be called that. The Sun will become a red giant, and will eventually blow off its outer layers, making a planetary nebula. The interior will then become a white dwarf.

I have calculated how much energy must be injected to destroy the Sun, and it's about 1.3 of the Earth's mass-energy.